Glykolyysiin

Glykolyysiin is the Finnish term commonly used for glycolysis, the central metabolic pathway that converts glucose into pyruvate to release energy for the cell. This process occurs mainly in the cytosol of cells and provides a rapid source of ATP and reducing equivalents, while supplying metabolic intermediates for various biosynthetic pathways.

The pathway consists of ten enzyme-catalyzed reactions, typically divided into two phases: an energy investment phase and a payoff phase. In the investment phase, glucose is phosphorylated and rearranged through a series of steps, including the actions of hexokinase or glucokinase and phosphofructokinase-1. In the payoff phase, fructose-1,6-bisphosphate is split into two glyceraldehyde-3-phosphate molecules, which are oxidized to produce NADH and ATP through substrate-level phosphorylation, ultimately yielding pyruvate.

Energy yield and regulation are central features of glycolysis. Net production from one molecule of glucose is two ATP and two NADH, with additional ATP produced later in cellular respiration depending on oxygen availability. Key control points are the enzymes hexokinase, phosphofructokinase-1, and pyruvate kinase, which respond to cellular energy status through allosteric regulation by molecules such as AMP, ATP, citrate, and fructose-2,6-bisphosphate. The pathway operates under aerobic or anaerobic conditions, but the fate of pyruvate differs: in the absence of oxygen, it is reduced to lactate or converted to ethanol in some organisms; with oxygen, it is transported into mitochondria for further oxidation via the pyruvate dehydrogenase complex and the citric acid cycle.

Glykolyysiin is essential for rapid energy production, particularly during high-demand situations, and provides intermediates for anabolic processes. Alterations in glycolysis are implicated in various physiological and pathological contexts, including cancer metabolism and metabolic disorders.